1) Field of the Invention
The present invention relates to a printed wiring board, a method of manufacturing the printed wiring board, a lead frame package, and an optical module.
2) Description of the Related Art
Conventionally, a semiconductor device, which is manufactured by connecting mounted semiconductor elements and wiring patterns using bonding wires and sealing the semiconductor elements and the wiring elements with resin, is known (see, for example, Japanese Patent No. 2528192). In addition, in a contact probe in which ends of wiring patterns formed on a surface of a film body project from the film body to be used as contact pins, it is known that the wiring patterns are formed by forming a photoresist layer, the wiring patterns and the contact pins are electrically connected by via-holes, and spaces for providing the via-holes are secured (see, for example, Japanese Patent Application Laid-open No. 2001-194387).
Among such semiconductor devices, for example, an optical module 1 shown in FIG. 22 includes a lead frame package 5, an intermediate member 7a, and a mounting block 8. The optical module 1 is manufactured as a product by connecting these components using bonding wires W and, then, sealing the components with electrically insulating synthetic resin, and integrating the components with a ferrule 9 having an optical fiber 9a. 
In this case, in the lead frame package 5, a printed wiring board (PWB) 2 and a lead frame 3 are molded with synthetic resin 4. On the other hand, the printed wiring board 2 has a micro-strip line structure in which an insulating layer 2b and fine wiring patterns 2d including conductor layers are sequentially formed on a conductor plate 2a formed in a predetermined shape. A mounted semiconductor element (an electronic circuit element) 6 and the wiring patterns 2d are connected by the bonding wires W. In the mounting block 8, an optical semiconductor element 8b on which light is made incident and from which light is emitted in a vertical direction with respect to a substrate surface, for example, a planar light receiving and emitting element (a vertical cavity surface emitting laser (VCSEL) or a planar photo diode (PD)) is provided on a silicon substrate 8a. The printed wiring board 2 is adapted to realize impedance matching in the optical module 1 and control deterioration in a signal transmission characteristic by adopting the micro-strip line structure.
When the components are connected by the bonding wires W in the optical module 1, regardless of the fact that the printed wiring board 2 of the micro-strip line structure is used, there is a problem in that a transmission characteristic for a high frequency signal is deteriorated because of an influence of inductance due to a length of the bonding wires W and process man-hour increases. In addition, the printed wiring board 2 and the lead frame 3, which constitute the lead frame package 5, and the intermediate member 7a, which is used with the lead frame package 5, are manufactured separately and then assembled. Thus, there is a problem in that manufacturing cost increases to make the optical module 1 expensive.
In the conventional optical module 1, the planar light receiving and emitting element 8b is fixed to a first surface 8a1 of the mounting block 8, and a conductor plate 7b is fixed on the intermediate member 7a in a surface 8a2 perpendicular to the first surface 8a1. A distal end of the conductor plate 7b is folded vertically downward along a facet of the intermediate member 7a to facilitate work for wire bonding between the conductor plate 7b and the first surface 8a1 of the mounting block 8. An end of the bonding wire W is bonded to this folded portion. Therefore, there is also a problem in that manufacturing cost of the intermediate member 7a increases.
To solve the problems described above, it is an object of the present invention to provide a printed wiring board that can control deterioration in a signal transmission characteristic due to a length of bonding wires by reducing wire bonding sections, can easily perform wire bonding work between the printed wiring board and a planar optical semiconductor element to be mounted, and can be manufactured at low cost, a method of manufacturing the printed wiring board, a lead frame package, and an optical module.